I have no idea how this should work except by decoding the file (decode_hrd_parameters() is not called in the H264 decoder so I assume there is no bitrate set in the video stream) but the fact that FFmpeg shows neither bitrate nor duration is definitely reproducible.

I just sent a patch to the ffmpeg-devel mailing list that would make the situation worse by setting a (not exactly correct) bitrate when decoding speex and therefore assuming a duration of ten minutes for the 10 seconds clip.

This file is invalid as it has been randomly truncated. The truncation is the reason why the duration is not successfully estimated. Its probably possible to get the duration out anyway but it seems that would either be tricky or slow